1. Field of the Invention
The present invention relates to an optical recording method and apparatus that records information onto an optical storage medium at a high speed by emitting a light beam to a recording layer of the storage medium. Further, the present invention relates to an optical storage medium that stores information recorded by using the optical recording method and apparatus.
2. Description of the Related Art
Recently, optical storage media, including CD-R (compact disk recordable), CD-RW (compact disk rewritable) and so on, become widespread. Each storage medium is provided for recording information thereon by focusing a light beam onto a recording layer of the medium and changing the phase of the recording layer material.
As disclosed in Japanese Laid-Open Patent Application No. 63-29336, an optical recording method that records information onto a recording layer of an optical recording medium by emitting light to the recording layer of the medium is known. In the optical recording method of the above document, a light source driving waveform is applied to a light source to control emission of a light beam to the recording layer of the medium based on a write data modulation method. Moreover, there is known an optical recording method that determines an optimum light source driving waveform (including the write power and the write pulse width), which is applied to the light source, based on a readout signal of the recorded information derived from a reflection light beam from the optical disk.
Further, several optical recording methods have been proposed for improvement of the quality of the write signal recorded on a rewritable phase-change storage medium. For example, Japanese Laid-Open Patent Application No. 63-266632 discloses such improvement method. In the conventional method of the above document, a pulse width modulation (PWM) method is utilized for application of a multi-pulse light source driving waveform to the light source to control emission of a light beam from the light source to a rewritable phase-change optical disk having a recording layer with a large crystallization speed. The conventional method provides the driving waveform that is effective in recording a long amorphous mark on the recording layer of the optical disk.
In addition, Japanese Laid-Open Patent Application No. 63-266633 and U.S. Pat. No. 5,150,352 disclose an optical recording method which eliminates positional variations of a mark edge and improves the jitter characteristics of an optical disk by applying a driving waveform including a front-end portion or a tail-end portion having an increased pulse width or with an increased power level to the light source.
Further, the rewritable compact disk standards (the orange book, part III, ver. 2.0) provide the recommended specifications of 1× to 4× linear velocity recording of the rewritable recording media. The linear velocities 1× to 4× according to the standards (the orange book, part III, ver. 2.0) range from 1.2 m/s to 5.6 m/s. The recording speeds of the media in this range require a relatively long time to record information onto the media. There is an increasing demand for a reliable CD-RW drive that is able to carry out error-free information recording with good write-erase characteristics at higher recording speeds. Preparations of high-speed specifications of range higher than 4× and up to 20× linear velocity recording for the rewritable compact disk standards are now under way. The linear velocities range higher than 4× and up to 20× according to the standards (the orange book, part III) range higher than 5.6 m/s and up to 28 m/s.
Accordingly, it is desirable to provide an optical recording method and apparatus that ensures good write/erase characteristics of the rewritable phase-change medium and retains the compatibility with the write-once storage medium when high-speed recording (equivalent to the range higher than 4× and up to 20× linear velocity recording) is performed. The conventional recording methods and devices of the above documents are not yet adequate to attain the goal.